00:02
So let's say we have a spherical raindrop that has a radius of 0 .65 millimeters.
00:10
So write this a 6 .5 times 10 to the negative 4 meters.
00:15
And it has a charge, a total charge, of negative 3 .6 picoculams distributed throughout the volume.
00:26
And we want to know what's the potential at the surface.
00:28
So first, let's find the electric field at the surface.
00:34
And so by gauss's lot, it'll be like, and let's, let me use a different letter for this.
00:38
Let's use a capital r.
00:39
So we know, like, our electric field times some distance or surface area at some distance r is going to be equal to the total charge enclosed by the sphere divided by epsilon or not.
00:51
So at the surface, we're basically just going to have the field of a point charge.
00:57
Right.
00:57
So this will be q over 4 pi r squared, epsilon, not.
01:04
And so if we plug in, well, we're looking for the potential.
01:09
So really, you know, at the surface, we'll have something like this.
01:16
And so our voltage is going to be the negative line integral of e.
01:22
And so this, and we're going to go from infinity to r...